Formation sampler



March 28, 1961 M. SURBATOVICH 2,976,940

FORMATION SAMPLER Filed Nov. 27, 1957 2 Sheets-Sheet 1 /5 INVENTOR. g M/LO saeeprowcy BY 7 M 7@. 2.

March 28, 1961 M. SURBATOVICH 2, 7

FORMATION SAMPLER Filed Nov. 27. 1957 2 Sheets-Sheet 2 FQRMATHQN SAMILER Milo Surbatovich, South Chicago, EL, assignor, by mesne assignments, to Dresser industries, Inc., Dallas, Tex., a corporation of Delaware Filed Nov. 27, 1957, Ser. No. 699,246

7 Claims. (Cl. 175-4 This invention relates to tools for taking samples of formations penetrated by earth boreholes, and more particularly to combined shaped charge and sampling projectile means for obtaining samples from sidewalls of earth boreholes drilled for producing fluids such as oil, gas, water, and the like.

In general, explosively activated earth borehole formation sampling tools employ an elongated gun body adapted to be lowered into a fluid-filled earth borehole on a suitable conductor cable. The gun body usually has a plurality of laterally directed gun bores in each of which is contained a propellant charge and a hollow or tubular shaped cutting projectile constructed to be propelled into penetrating impact with the adjacent formation to be sampled. Each of the projectiles usually is held captive to the gun body, both before and after firing, by a flexible Wire or cable by means of which the projectile, after firing, can be dislodged from the surrounding formation and retained in attachment to the gun body for. subsequent retrieval from the borehole together with a captured sample.

The sampling of hard sidewall formations in fluidcontaining boreholes at great depths and under high fluid pressures presents very difficult problems. Satisfactory samples free from excessive fracturing or compaction are needed for analysis and testing to determine the original conditions prevailing in the formation zones from which the samples are taken. Prior art sampling tools described in the previous paragraph, sometimes fail to satisfactorily penetrate very hard sidewall formations to a sufficient depth to obtain a sample of adequate size for analysis. At times the sample recovered from the hollow cutting projectile is unduly compacted and does not give an accurate indication of the permeability of the sidewall formation sampled. At still other times the recovered sampie is unduly fractured as a result of percussion forces and pressure build-up in the projectile and accurate laboratory analyses cannot be made thereon.

Accordingly, it is an object of this invention to provide a sidewall formation sampler which is free of all the hereinbefore described disadvantages and defects.

Another object is to provide a sidewall sampler which will be more reliable than prior art samplers in obtaining a satisfactory sample of a very hard sidewall formation.

A further object is to provide a sampler which will reliably capture a large sample of very hard sidewall formation without excessive compaction or fracturing.

Briefly stated in general terms the objects of this invention are attained by sidewall formation sampling apparatus employing a shaped charge or charges to pene trate the sidewall formation in a predetermined manner around a portion thereof to be sampled. The penetration preferably is made in a manner to partially undercut the portion of sidewall to be sampled and to remove some of the surrounding sidewall formation material without completely freeing the portion to be sampled from the sidewall. Simultaneously, or slightly after the discharge of the shaped charges, a sampling projectile is propelled into the portion of sidewall formation to be sampled. Because that portion of the sidewall is undercut, the sampling projectilemore readily cuts away parts of the formation adjacent the undercut sidewall portion. As the sampling projectile penetrates the undercut formation, it cap.- tures a sufiiciently large sample without unduly compacting or fracturing the same. The sampling projectile and captured sample also are more readily freed from the sidewall formation by a retrieving cable as a result of the under cutting efiect produced by the shaped charges.

A more detailed description of a preferred embodiment of the invention is given hereinafter with reference to the n drawings wherein: I

Figure 1 is an elevational view showing a core collects ing tool containing two sampling units, disposed in a borehole;

Figure 2 is a view similar to that of Figure 1 drawn to a somewhat larger scale and showing the sampling units in partial longitudinal section;

Figure 3 is a partial, enlarged longitudinal sectional view showing details of a sampling unit in place in the tool before it has been actuated for capturing a sample; and

Figure 4 is a longitudinal sectional view taken along line 4-4 of Figure 3 showing the orientation of the shaped charges employed to undercut the sidewall formation.

The sampling tool shown in the drawings comprises an elongated gun body 10 shown in Figure 1 suspended in operating position in an earth borehole 11 by a conductor cable 12. The gun body comprises an upper portion 13 which houses electrically activated switching mechanism (not shown) for sequentially, electrically firing individual sampling units when more than one sampling unit is incorporated in the same gun body; a second portion 14 serving as an upper connector; a third portion 16 which is the top sampling unit; a fourth portion 16a which is a second or bottom sampling unit, depending upon the number of such units in the gun body 10; por tion 17 which is the lower connector; and bottom portion 18 which is a bull plug. A suitable laterally extending backing bow spring 19 is attached at its upper end to the upper connector portion 14 and at its lower end to the lower connector portion 17 of the gun body. The pur pose of spring 19 is to position the gun body. 10 eccentrically with respect to the borehole axis so that the side of the gun body, opposite the spring 19, from which the sampling units are directed, is held firmly against the side of the borehole 11.

A conventional electrical switching system such as the one disclosed in US. Patent 2,210,125, to F. L. Raymond et al. may be used to control sequential firing of the individual sampling units of the tool.

The cable 12 contains an insulated electrical conductor (not shown) for electrically interconnecting current supply and control means located outside the top of the borehole 11 with the beforernentioned electrically activated switching mechanism housed within the upper portion 13 of the gun body 10. The wiring for firing each group of explosive shaped charges in combination with a sampling projectile propellant powder cartridge, when two or more sampling units are employed on a gun body, such as the two units shown in Figure 1, includes a num-. ber of sets of conductors 15, as shown in Figure 3, one set for each such unit combination. Each of these sets of conductors is electrically connected to the switching mechanism housed within upper portion 13 of the tool where contact is made selectively with the conductor in cable 12. through the switching mechanism. Upper sampling unit 21 is mounted in a cavity 22 formed in the side of portion 16 of the gun body Ill. The cavity converges. inwardly to a circular bottom 23. A cylindrical barrel bore 24 of smaller inside diameter than the diameter of bottom 23 extends inwardly from the bottom 23, transversely toward the opposite side of gun body but terminates short thereof'in an annular shoulder 27. An internally threaded bore 26 of smaller inside diameter than cylindrical barrel bore 24 in turn extends coaxially inwardly from the annular shoulder 27 of the barrel bore, and in turn a recess 2801: still smaller diameter than bore 24 extends coaxially inwardly from the annular shoulder 29 formed at the inner end of the threaded bore 26. The walls and inner end of recess 28 are lined with anelectrical insulating lining 32.

An electrical contact plate 31 is mounted flush against the insulation 32 at the inner end of the recess 28. This plate is electrically insulated from the gun body but is electrically connected to an insulated electrical conductor 33 as indicated at 34. The conductor 33 is tightly mounted in the gun body 10 by a sealing nut 36 through which the conductor passes. The sealing nut is threadedly mounted in a recess or groove 37 cut in the gun body so that the conductor 33 can make a fluid tight entrance into the recess 28 for connection to the contact plate 31. Nut 36 prevents high pressure fluid in borehole 11 from entering recess 28 and fouling or short circuiting a contact pin igniter 38 which is hereinafter more fully described.

ceive an O-ring 71 to seal borehole fluid from. contact pin igniter 38 and adjacent powder cartridge 72 in powder chamber 73. Retrieving cable 51 is wound spirally against the inside wall of powder chamber 73 and a powder cartridge 72 is placed inside the cable spiral, The assembled sampling projectile is loaded into cavity or barrel 24 as best shown in Figure 3. Shear pins 74 pass through aligned radial holes 76 and 77, respectively, where the rear end of base section 56 overlaps the front end of cable attachment plug 41, to retain the sampling projectile in the gun body.

A group of shaped charges 78 is mounted in the cavity 22 around the core section 54 of the sampling projectile 53. The axes 79 of the shaped charges preferably, although not necessarily, are directed to converge at a point 81 external of the gun body and the sampling projectile and on the axis 82 of the sampling projectile. The

. angles between the axes 79 of the shaped charges 78 The stem of the contact pin igniter 38 is mounted through a passage 39 drilled axially through an externally threaded cable attachment plug 41. The igniter head 42 of the igniter pin 38 is seated in a conical cavity 43 in the front of the plug 41 and the threaded, rear contact end portion 44 of the stem 35 protrudes fromthe rear end of the plug 41. A contact spring 46 is mounted on the rear threaded end portion 44 of the stem 35 and in turn the whole contact pin igniter assembly is held in the plug 41 by means of a nut 45 threaded on the said rear threaded end 44 of the stem 35. When the plug 41 is threaded into' the internally threaded bore 26, the spring 46 is pressed resiliently against contact plate 31 to securely establish electrical connection between the plate and the contact pin igniter 38. g v

The general construction of the igniter 38, 42 is shown in Patent No. 2,649,736 issued to Robert A. Phillips.

. The cable attachment plug 41 is provided with a retaining notch formed by a radial slot 47 extending from the forward face ofthe plug into a radial bore 48, the notch thereby formed being adapted to retain a ball 49 and the axis 82 of the sampling projectile preferably are chosen such that for a given penetrating power and charge of the shaped charges, the borehole formation will be undercut as indicated at 83 in Figure 2. The undercut portion 84, which preferably is not completely freed from the formation wall, is of greater diameter than the diameter of the bore of front coring section 54 of the sampling.

projectile 53. In such case the projectile can take a fullsizedcut out of the thus partially freed formation sam ple which will wedge firmly within the bore of the coring section 54.

The shaped charges are held in the desired position surrounding the forward end portion of the coring section 54 of the sampling projectile 53 in a carrier 86 of any suitable design. In the embodiment shown in the drawings the carrier consists of two spaced parallel annular members 87 and 88 provided with aligned circular apertures and mounted on opposite ends of a cylindrical section 90, to form an annular assembly having a U-shaped crosssection. The annular members 87 and 88 are provided with apertures 91 and 92 to hold therein the individual shaped charges of the group 78. The radial distance'from axis 82 of the sampling projectile to the center of apertures 92 of annular member 88 is made greater than the similar radial distance to the centers of the apertures 91 swaged onto the inner end of a retrieving cable 51 which extends forwardly through the slot 47. The ball is lodged in the notch before the 'plug 41, containingthe contact pin igniter assembly, is screwed into the internally threaded hole 26 in gun body 10. A similar ball is swaged onto the outer end of cable 51, and is lodged in an. attachment nut 52'. The nut 52 is provided with a radial notch 52a and a central socket 52b into which the ball and cable are fitted before the nut is threaded into the base of a sample projectile 53.

The sampling projectile 53 is generally cylindrical in shape and is made up of a front core cutting section 54 and a rear base section 56 joined together end to end by a threaded connection at 62. The core cutting section 54 is hollow and converges forwardly at 57 and 58 on the forward exterior surface thereof to provide a blunt front end having a relatively sharp annular cutting edge at 59. These characteristics of the core section make for strength and sharpness required to cut and penetrate very hard sidewall formations. Radial fluid escape holes 61 are drilled through the cylindrical wall portion of the core cutting section 54 to provide exits for borehole fluid when the section is propelled into the wall of the borehole to cut a core sample from the wall formation.

An internally threaded .bore 67 is formed coaxially in plug portion 64 to threadedly receive attachment nut52 and ball 50, as .hereinbefore mentioned. Hollow cylindrical body portion 68 of the base section is provided with an annular groove 69 near the rear endthereof to reof annular member 87 such that the shaped charge units are directed at the desired angle, as mentioned herein above, at point 81 in the borehole wall. The inside diameter of the cylindrical section 90 is made slightly larger than the outside diameter of sampling projectile 53 so that the cylindrical section can be mounted around thc projectile with a light press fit upon the exterior of the coring section 54 thereof.

The second, and any successive sampling assemblies, are constructed in the manner described hereinabove in connection with Figure 3. Below the lowermost sampling assembly is formed a plain cavity 96' similar to cavity 22 but without any sampling projectile bore. The purpose of cavity 96 is to accommodate the lowermost sampling projectile, such as projectile 94, Figure 2, after it has been retrieved from a borehole wall. The retrieved sampling projectile hangs at the outer end of a retrieving cable as shown at'97, and the cable hangs over a shelf 98. The shelf 98 is rounded to avoid damage to the cable by sharp edges. A similar she1f99 is formed between adjacent sampling'units so that the retrieved sampling projectile from an upper sampling assembly can safely hang overthe shelf and be retained in the cavity of the next lower sampling assembly.

The gun body and each sampling assembly are prepared for actual use in a borehole by first installing a contact. plate 31 in the recess 28 lined with insulation 32. The contact plate is electrically connected to the proper conductorsuch as conductor 33, as shown in Figure, 3. The sampling projectile 53 is made up by threading base section 56 into core cutting section 54 as.

shown at 62 in Figure 3. Ball 50 on the outer end of retrieving cable 51 is inserted in the socket 52b of attache ment nut 52 with cable 51 extending through notch 52a. Attachment nut 52 is screwed into base section 56 as shown at 67 in Figure 3. Retrieving cable 51 is wound spirally against the inside wall of powder chamber 73 in base section 56 and a powder cartridge 72 is placed' inside the spiral cable.

Contact pin igniter 38 is mounted in attachment plug 41, as described hereinabove. Ball 49 on the inner end of retrieving cable 51 is mounted in radial bore 48 with the cable 51 extending through radial slot 47. The forward end of attachment plug 41 is fitted into the rearward end of base section 56 and adjusted so that radial holes 76 of the base section are brought in alignment with radial holes 77 of the attachment plug. Shear pins 74 are inserted into the aligned holes to attach the attachment plug 41 to the assembled projectile 53. Theresulting sampling unit is mounted in the gun body by screwing attachment plug 41 into the gun body at internally threaded bore 26. A shaped charge carrier 86 is loaded with shaped charges 78, as described hereinabove.

After each sampling unit is loaded, upper connector 14, lower connector 17 and bull plug 18 are attached to the gun body. Backing spring 19 then is attached to the gun body by brackets 101 and 102. A blasting cap 103 is connected to an explosive cord 104 of each shaped charge unit, which, in turn, is mounted on the booster portion 1% of the shaped charge unit 78 by threading through the booster portions as shown. Electrical connection is made from each contact pin igniter conductor 33 in each sealing nut 36 to each plate 31 and each contact pin igniter 38 by threading the nut 36 into the passage 37 formed through the gun body 10. Each contact pin igniter 38 is connected in parallel with each blasting cap 133 which in turn is connected to electrically activated switching mechanism (not shown) for electrically firing individual sampling units.

The assembled sampling tool is lowered to the point at which it is desired to take a sample in a borehole. The lowermost sampling unit is fired first. Although both the shaped charge units and the sampling projectile are fired at the same time, because they are connected in parallel with respect to each other, the inertia of the heavy sampling projectile 53 causes it to take effect on the borehole formation somewhat later than the shaped charge units. Thus the undercutting action of the shaped charge units is substantially completed before the sampling projectile strikes the undercut formation to capture a sample thereof inside the hollow portion of core section 54.

By reason of the hard borehole formation being previously undercut at 83, the sampling projectile 53 is capable of penetrating the formation to a maximum extent to capture a full-sized sample without excessive compaction or fracturing thereof. Also, by reason of the undercutting at 83, the imbedded sampling projectile can be more readily dislodged from the formation by raising the sampler and pulling on retrieval cable 51. The dislodged sampling projectile containing the captured sample drops downwardly into the gun body cavity 96. The sampler tool then is moved to the next point at which it is desired to obtain a sample. At this second point the sampling unit next above is selectively fired so that the retrieved sampling projectile can occupy the cavity of the just previously fired sampling unit next in line below.

While the invention has been herein illustrated and described in what is now considered to be a preferred embodiment, it is to be understood that the invention is not limited to the specific details thereof, but covers all changes, modifications and adaptations within the scope of the appended claims.

What is claimed is:

1. A sidewall sampler comprising: shaped charge means arranged for penetrating a sidewall formation to form an annular ruptured pattern around a portion thereof to be sampled; cup-like sampling projectile means. associated with the shaped charge means and arranged to be propelled axially in the same general direction as the direction of penetration of said shaped charge means for penetration of said formation within the annular ruptured pattern; propulsion means associated with the sampling projectile means for propelling the same into such sidewall portion; means for discharging the shaped charge means and actuating the propulsion means of the sampling projectile means; and means for retrieving the sampling projectile and sidewall sample contained therein after the projectile hasbeen propelled into such sidewall portion.

2. A sidewall sampler comprising: shaped charge means arranged in a pattern around a central point for penetrating a sidewall formation. to form an annular ruptured pattern around a portion thereof to be sampled; cup-like, tubular sampling projectile means having a bore extending axially therethrough associated with the shaped charge means and arranged to be propelled axially in the same general direction as the direction of penetration of said shaped charge means for penetration of said formation within the annular ruptured pattem; propulsion means associated with the sampling projectile means for propelling the same into such sidewall portion; means for discharging the shaped charge means and actuating the propulsion means of the sampling projectile means; and means for retrieving the sampling projectile and sidewall sample contained therein after such projectile has been propelled into the sidewall portion.

3. A sidewall sampler comprising: a group of shaped charges arranged in a curved pattern for penetrating a sidewall formation to form an annular ruptured pattern around a portion thereof to be sampled; cup-like sam: pling projectile means disposed inside the curved pattern of the shaped charges and arranged to be propelled axially in the same general direction as the direction of penetration of said shaped charges for penetration of said formation within the annular ruptured pattern; propulsion means associated with the sampling projectile means for propelling the same into such sidewall portion; means for discharging the shaped charges and actuating the propulsion means of the sampling projectile means; and means for retrieving the sampling projectile and sidewall sample contained thereinafter the projectile has been propelled into such sidewall portion.

4. A sidewall sampler comprising: a group of shaped charges arranged in a curved pattern for penetrating a sidewall formation to form an annular ruptured pattern around a portion thereof to be sampled; cup-like, tubular sampling projectile means having a bore extending axially therethrough disposed inside the curved pattern of the shaped charges and arranged to be propelled axially in the same general direction as the direction of penetration of said shaped charges for penetration of said formation within the annular ruptured pattern propulsion means associated with the sampling projectile means for propelling the same into such sidewall portion; means for discharging the shaped charges and actuating the propulsion means of the sampling projectile means; and means for retrieving the sampling projectile and sidewall sample contained therein after the projectile has been propelled into such sidewall portion.

5. A sidewall sampler comprising: a group of shaped charges arranged in a circular pattern for penetrating a sidewall formation around a portion thereof to be sampled; cup-like cylindrical sampling projectile means having a bore extending axially therethrough disposed inside the curved pattern of the shaped charges and arranged to be propelled axially in the same general direction as the direction of penetration of said shaped charges; propulsion means associated with the sampling projectile means for propelling the same axially into such sidewall portion; means for discharging the shaped charges and actuating the propulsion means of the sampling projectile means; and means for retrieving the sampling projectile and sidewall sample contained therein after the projectile has been propelled into such sidewall portion.

6. A sidewall sampler comprising: a group of shaped charges arranged in a circular pattern and aimed at a common target adjacent the sampler for undercutting a sidewall formation around a portion thereof to be sampled; cup-like, cylindrical sampling projectile means having a bore extending axially therethrough mounted centrally of the curved pattern of the shaped charges and arranged to be propelled axially at the common target; propulsion means associated with the. sampling projectile means for propelling the same axially into such sidewall portion; means for discharging the shaped charges and actuating the propulsion means of the sampling projectile means substantially.simultaneously; and means for retrievingthe sampling projectile and sidewall sample contained therein after the projectile has been propelled into the sidewall.

7. A sidewall sampler comprising: cup-like sampling projectile meansarranged for axially penetrating a sidewall formation; shaped charge means arranged peripherally around said sampling projectile means and aimed for penetration in' the same general direction for lformingian annular ruptured pattern in such sidewall References Cited in the file of this patent UNITED STATES PATENTS 2,757,611 Church et al. Aug. 7, 1956 2,802,041 Schneersohn Sept. 3, 1957 

